Low-loss closed-loop supply system for transferring liquified gas from a large container to a small container

ABSTRACT

A liquified gas is transferred from a supply tank to a saddle tank by gravity flow. After a predetermined amount of the liquified gas has been transferred, gravity flow is stopped and pressure is equalized between the saddle tank and the container to be filled. Thereafter, vapor from the container flows into the supply tank causing liquified gas to flow from the saddle tank into the container. After the container has received a predetermined amount of liquified gas, liquid flow ends and pressure is equalized between the supply and saddle tanks. 
     BACKGROUND OF THE INVENTION

This invention relates to a method and apparatus for filling smallcontainers from large containers and more particularly to a method andapparatus for filling a small container with liquified gas from a largecontainer, without the loss of gas vapor.

It is often necessary to transfer liquified gases from larger containersto smaller containers. For example, oxygen converters used forconverting liquified oxygen (LOX) to a gas for use by the crews of highaltitude aircraft are usually filled from larger tanks; and, in thisregard, objects of this invention are to provide a new and improvedmethod and apparatus for transferring a liquified gas from one containerto another.

Many of the transferred gases are quite volatile and tend to boil offrapidly during conventional transfer methods. Hence, because many ofthese gases are also quite expensive to produce, it is another object ofthis invention to provide a particularly low-loss method of transferringa liquified gas from a large container to a small container.

Some liquified gas vapors that are released during conventional transfermethods are highly dangerous because they readily support combustion. Inaddition, flammable gases such as hydrogen and natural gas often must betransferred from large containers to small containers for use atparticular locations. If gas vapors are released during the transfer offlammable gases, they produce a highly dangerous environment because ofboth combustability and possibly inhalation. Consequently, it is anotherobject of the invention to provide a safer method and apparatus forperforming the desired transfer without vapor of the transferred gasboiling off into the atmosphere.

It is still a further object of this invention to provide a new methodand apparatus for transferring cryogenic fluids in a manner which doesnot require expensive cryogenic pumps so as to further reduce boil offlosses.

SUMMARY OF THE INVENTION

In accordance with principles of this invention, the liquified gas isfirst transferred from a supply tank to an intermediate tank by gravityflow. After a predetermined amount of the liquified gas has beentransferred in this manner, pressure is equalized between theintermediate tank and the container to be filled. Thereafter, pressurefrom the container is bled down into the supply tank causing liquifiedgas to flow from the intermediate tank into the container. Transfer isended after the container has received a desired amount of liquifiedgas. Thereafter, pressure is equalized between the supply andintermediate tanks, and the cycle is repeated to fill a secondcontainer.

In accordance with other principles of this invention, the supplycontainer and the intermediate container are vacuum insulated, as arethe lines interconnecting the supply tank, the intermediate tank and theconverter so as to further conserve gas by preventing boil-off loss.

It will be appreciated from the foregoing summary that the inventionprovides an uncomplicated method and equally uncomplicated apparatus fortransferring a liquid gas from a supply container or tank to a smallercontainer or converter with low vapor loss. By utilizing the pressuresin the tanks and gravity to cause the liquified gas to flow, the needfor an expensive cryogenic pump is eliminated. In addition, the highboil-off associated with the use of cryogenic pumps is also eliminated.

While the illustrated use of the herein described invention is totransfer LOX from a supply container to a converter, and thus reduce thevapor danger associated with such transfers, it will be appreciated thatthe invention can be utilized to transfer other types of liquifiedgases. For example, the invention can be utilized to transfer flammableliquified gases, such as hydrogen and natural gas.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing objects and many of the attendant advantages of thisinvention will become more readily appreciated as the same become betterunderstood when taken in conjunction with the accompanying drawings,wherein:

FIG. 1 is a schematic diagram illustrating a preferred embodiment of theinvention;

FIGS. 2, 3, and 4 are schematic diagrams illustrating the sequence oftransfer between the supply container and the container to be filled;

FIG. 5 is a schematic diagram of a condensing system for use with theembodiments of the invention illustrated in FIGS. 1 and 6; and,

FIG. 6 is a schematic diagram illustrating an alternate embodiment of aportion of the structure illustrated In FIG. 1.

DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 illustrates a preferred embodiment of the invention andcomprises: a supply tank 11; an intermediate tank 13; a converter 15;four primary valves 17, 18, 19 and 21; four secondary valves 23, 25, 27and 29; an automatic valve 31; two pressure relief valves 33 and 35; arupture disc 37; and, three pressure indicators designated P1, P2 andP3.

The supply tank has a liquid input/output line 39 and a vaporinput/output line 41; the intermediate tank 13 which is of thesaddle-type has a liquid input/output line 43 and a vapor input/outputline 45; and, the converter has a liquid input/output line 47 and avapor input/output line 49. The liquid input/output line 39 of thesupply tank is connected by pipes through the first secondary valve 23and a filter 51 to an input connection. The input connection allowsliquified oxygen (or another liquified gas, as the case may be) to beinserted into the supply tank 11 to fill that tank. The liquidinput/output line 39 of the supply tank 11 is also connected by pipesthrough the first primary valve 17 and a first supply saddle couplingmember 53 to the liquid input/output line 43 of the saddle tank 13. Thevapor input/output line 45 of the saddle tank 13 is connected by pipesthrough a second supply/saddle coupling member 55 and the second primaryvale 18 to the vapor input/output line 41 of the supply tank 11.

A pressure sensor 57, located in the saddle tank, is connected by pipesthrough a heat exchanger coil 58, a pressure regulating valve 59, andthe second secondary valve 25 to the pipe line connecting the vaporinput/output lines of the saddle and supply tanks 11 and 13. The samepipe line is also connected to P2 and through the first pressure reliefvalve 33 to a vent output. The vapor input/output line 41 of the supplytank 11 is also connected by a pipe through the third secondary valve 27to the vent output, through the second pressure relief valve 35 to thevent output and through the rupture disc 37 to the vent output. Inaddition, the vapor input/output line 41 of the supply tank 11 isconnected to P1. The liquid input/output line 39 of the supply tank 11is connected by a pipe through the fourth secondary valve 29 and a heatexchanger coil 61 to the vapor input/output line 41 of the supply tank11.

The liquid input/output line 43 of the saddle tank 13 is connected bypipes through a saddle-converter coupling member 63 to a first terminalon one side of the automatic valve 31. The liquid input/output line ofthe supply tank 39 is connected by pipes through the third primary valve19 and a supply/converter coupling element 65 to a second terminal onthe same side of the automatic valve 31. The fourth primary valve 21 isin a pipe connected across the first and second terminals on this sameside of the automatic valve 31. In addition, P3 is connected to the pipeline that connects the liquid input/output line 39 of the supply tank 11to the automatic valve 31. The other side of the automatic valve 31 isconnected by pipes to the liquid and vapor input/output lines 47 and 49of the converter 15.

All of the pipe lines connecting the supply tank to the saddle tank andconnecting the supply and saddle tanks to the converter are vacuuminsulated to prevent undesirable boil-off. The remaining lines are notillustrated as being insulated, however, they may be insulated, ifdesired. The insulated lines connecting the supply tank and the saddletank and the converter form the primary apparatus of the invention andare utilized to carry out the method as hereinafter described withrespect to FIGS. 2, 3 and 4. The remaining lines provide a means forfilling the supply tank as well as for venting the various vapor linesand tanks as necessary to the normal operation of a liquified gassystem, as will be understood by those skilled in the art. For example,the first pressure relief valve 33 provides pressure relief for thesaddle tank. Similarly, the second pressure relief valve 35 providespressure relief for the supply tank. The heat exchanger coil 58 and 61allows vaporization of the liquid to build pressure in their respectivesaddle and supply tanks, when desired.

Turning now to a description of the operation of the apparatusillustrated in FIG. 1 for carrying out the method of the invention; itis initially assumed that the pressure in both the supply tank and thesaddle tank is zero psig. In addition, it is assumed that the pressurein the converter tank is in the range of 50-100 psig. Similarly, it isassumed that the temperature of the converter is substantially atliquified oxygen temperature. Moreover, in accordance with theprinciples of the invention, the saddle tank is at a lower elevationthan the supply tank.

The first step of the method of the invention is the opening of thefirst and second primary valves 17 and 18 (FIG. 2). When this occurs,the liquid flows by gravity from the supply tank 11 through the firstvalve 17 into the saddle tank and vapor flows from the saddle tankthrough the second valve 18 into the supply tank. When the desiredamount of liquid has flowed from the supply tank to the saddle tank, thefirst and second primary valves 17 and 18 are closed. This liquid-vaporflow increases pressure slightly in both tanks to about 3-5 psig, forexample.

Next the converter 15 is coupled to the system and the automatic valve31 and the fourth primary valve 21 are opened. In accordance with thisstep of the method (FIG. 3), pressure is equalized between the converterand the saddle tank through the saddle/converter coupling element 63.When the pressure in these two tanks has equalized, they will both be ata value of, for example, 30 psig, depending upon the size of the tanks.

In accordance with the method of the invention, after equalizationbetween the converter and the saddle tank has been completed, the fourthprimary valve 21 is closed and the third primary valve 19 is opened(FIG. 4). When the third primary valve is opened and the fourth primaryvalve is closed, the pressure differential between the converter 15 andthe supply tank 11 causes vapor to flow from the converter 15 to thesupply tank 11. This action causes liquid to flow from the saddle tank13 into the converter 15. Any vapor produced by this liquid flow passesinto the supply tank 11 and bubbles through the liquid phase in thesupply tank to cause turbulence in the supply tank which reduces thermalstratification and undue pressure rise in the supply tank. To preventreverse vapor flow from the converter 15 to the saddle tank 13 a one-wayvalve 67 is included in the automatic valve 31.

When the converter has filled to a satisfactory level, the third primaryvalve 19 is closed. In addition, the automatic valve 31 is closed andthe converter is disconnected. The second primary valve 18 is thenopened to bring the pressure in the saddle tank down to the pressure inthe supply tank. Because of the accumulation of vapor in these insulatedtanks, the pressure in the tanks will rise, up to 20 psig, for example.

When it is desired to fill another converter from the supply tank, theforegoing cycle is repeated. However, in this case, the supply tankstarts at an initial pressure of about 20 psig. Hence, at the end of thefilling of the second converter, the pressure in the supply and saddletanks will be about 40 psig, for this example. Consequently, ultimately,it will become necessary to reduce the pressure in the supply and saddletanks.

Pressure in the supply tank 11 and intermediate tank 13 is, preferably,reduced by either of two methods. In accordance with the first method,these tanks are removed to a remote area and bled down by allowing theoxygen vapor to be vented into the atmosphere. In accordance with thesecond method, the tanks may be provided with condensing loops 70 and 71in FIG. 5 for circulating liquified nitrogen from a nitrogen supply tank72.

In the above regard, liquified nitrogen from the condensing fluid tank72 is directed by means of suitable valving, not shown, throughinsulated lines 74 and 75 into the loops 70 and 71 where the tank vaporsare condensed in the tanks themselves. The nitrogen vapors are thenvented to the atmosphere as illustrated in the FIG. 5 schematic. In thismanner the pressures in the supply and saddle tanks are not only reducedto substantially zero but the tank vapors are condensed and recoveredwithout the possible danger of their being released into the atmosphere.

When the method of the invention is used with the above describedstructure vapor from the converter 15 flows out of end 78 of line 43after the converter is coupled to the system and valves 21 and 31 areopened. Hence, the vapor from 78 flows upwardly through the saddletank's liquid to cause turbulence which, in many cases is undesirable.Note in this regard, that the intermediate tank 13 is not a long term"storage" tank and, therefore, does not have the thermal stratificationproblems of the supply tank 11. Consequently, although it can beadvantageous for vapor to bubble through the liquid phase of the supplytank, this is not generally the case with the intermediate tank.

The FIG. 6 structure eliminates both the bubbling of vapor from theconverter 15 through the saddle tank's liquid phase and eliminates theneed for the FIG. 1 embodiment's valve 21. In this regard, the FIG. 6embodiment includes a vacuum insulated line 80 extending between point82 on the supply tank's link 39 and point 84 at the top of thesaddle-type intermediate tank 13. The line 80 includes a one-way checkvalve 86 for permitting vapor to flow only in the direction of the arrow(toward point 84); and does not include either a valve such as 21 or aline extending between the converter's liquid-input and vapor-outputlines. The remainder of the FIG. 6 embodiment is the same as FIG. 1 andwill not be further described.

The operation of the FIG. 6 embodiment is similar to that of FIG. 1. Inthis regard, liquid is first transferred from the supply tank to theintermediate tank and the pressure therebetween is equalized before thesupply and saddle tanks are isolated. Next, the converter is coupled tothe system at coupling elements 63 and 65; and vapor from converter 15flows into the top of the saddle tank 13 through line 80 and the checkvalve 86. When the pressure in these tanks in thusly equalized, valve 19is opened to permit vapor from converter 15 to flow into the supply tank11 in the same manner as was described in connection with the firstembodiment. Similarly, as the pressure in the converter drops, fluidfrom the saddle tank is forced through line 43 and check valve 67 intothe converter. It should be noted that the check valve 86 prevents thevapor from the saddle tank from flowing at this time into either thesupply tank or the converter. In other respects, operation of the twoembodiments is the same.

It will be appreciated from the foregoing description that the inventioncomprises a method and apparatus for filling a small container orconverter from a large container or supply tank. In general, the methodcomprises the steps of: equalizing the pressure between first and secondvessels in the supply system; transferring liquid from the first vesselto the second vessel and transferring vapor from the second vessel tothe first vessel; isolating the first vessel from the second vessel;equalizing the pressure between the second vessel and the container forreceiving the liquified gas; isolating the vapor phase of the secondvessel from the vapor phase of the container for liquified gas;connecting the first vessel to the container; connecting the secondvessel to the container for liquified gas so that liquid from saidsecond vessel flows into said container while vapor from the containerflows into the first vessel; and, isolating the container from saidfirst and second vessels. It will be appreciated that this method hascertain advantages in that it eliminates the necessity for pumping theliquified gas from one vessel to a second vessel. In addition iteliminates some of the other inherent disadvantages of former suchsystems. Moreover, because constant interconnections are provided, vaporloss is greatly reduced over prior art container filling systems; andthe method also has the advantage of reducing stratification in thesupply tank.

In addition to being an uncomplicated method, the invention alsoprovides for safe recovery of the supply tank vapors; and providesuncomplicated apparatus for carrying out the method in that only a smallquantity of interconnecting lines and valves are utilized to carry outthe method of the invention.

While a preferred embodiment of the invention has been illustrated anddescribed, it will be appreciated by those skilled in the art and othersthat various changes can be made therein without departing from thespirit and scope of the invention.

For example, although the vapor condensation step has been described interms of both supply tank 11 and saddle tank 13, it will be apparentthat were the vapor phases of the two tanks are connected together as byvalve 18, the condensation step can take place by connection of eithertank into one of the loops 70.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A low-loss method offilling a container for liquified gas from a supply system comprisingthe steps of:transferring liquid from a first vessel into a secondvessel, and transferring vapor from said second vessel to said firstvessel whereby the pressure between said first and second vesselsremains equalized as said liquid is transferred; isolating said firstvessel from said second vessel; equalizing the pressure between saidsecond vessel and said container for liquid gas; connecting said firstvessel to said container for liquified gas to permit vapor to flowtherebetween; connecting said second vessel to said container forliquified gas so that said liquid from said second vessel flows intosaid container for liquified gas, and maintaining the connection betweensaid first vessel and said container for liquified gas to permit vaporfrom said container for liquified gas to flow into said first vessel. 2.A low-loss method of filling a container for liquified gas from a supplysystem as claimed in claim 1 including the additional stepof:disconnecting said container for liquified gas from said first andsecond vessels.
 3. A low-loss method of filling a container forliquified gas from a supply system as claimed in claim 1 wherein saidliquified gas is liquid oxygen.
 4. The method of claim 1 including thestep of connecting the vapor phase of said container to the vapor phaseof said second vessel during said step of equalizing the pressurebetween said second vessel and said container.
 5. The method of claim 1including the step of isolating the vapor phase of said second vesselfrom the vapor phase of said container after said step of equalizing thepressue between said second vessel and said container.
 6. A low-lossmethod of filling a container for liquified gas from a supply system asclaimed in claim 1 wherein said liquid is transferred from said firstvessel into said second vessel by gravity.
 7. A low-loss method offilling a container for liquified gas from a supply system as claimed inclaim 6 wherein said liquified gas is liquified oxygen.
 8. The method ofclaim 1 including the step of condensing vapors from at least one ofsaid first and second vessels.
 9. The method of claim 8 including thestep of returning the condensate to the liquid phase of at least one ofsaid first and second vessels.
 10. The method of claim 1 including anadditional equalization step after said container is filled wherein thevapor phases of said first and second vessels are connected to bring thepressure of said second vessel down to the pressure of said firstvessel.
 11. The method of claim 10 including the step of condensingvapors from at least one of said first and second vessels.
 12. Themethod of claim 11 including the step of returning the condensate to theliquid phase of at least one of said first and second vessels.
 13. Apump-free low-loss supply system for filling a container for liquifiedgas comprising:a supply tank for housing said liquified gas; anintermediate tank for temporarily storing said liquified gas; firstinterconnecting means for interconnecting said intermediate tank to saidsupply tank for allowing liquid to flow from said supply tank to saidintermediate tank and vapor to flow from said intermediate tank to saidsupply tank; and second interconnecting means for interconnecting saidintermediate tank and supply tank to said container so as to allow gasfrom said container to flow from said container to said intermediatetank and thereafter allow liquid from said intermediate tank to flowinto said container while vapor from said container for liquified gasflows into said supply tank, said liquid being transferred pump-freefrom said supply tank to said container.
 14. A low-loss supply systemfor filling a container for liquified gas as claimed in claim 13 whereinsaid liquified gas is liquified oxygen.
 15. A low-loss supply system forfilling a container for liquified gas as claimed in claim 13 whereinsaid intermediate tank is mounted at a lower elevation than said supplytank whereby liquid flows from said supply tank to said intermediatetank by gravity.
 16. A low-loss supply system for filling a containerfor liquified gas as claimed in claim 15 wherein:said supply tankincludes an input/output vapor line and an input/output liquid line;said intermediate tank includes an input/output vapor line and aninput/output liquid line; and, said first interconnecting meanscomprises: a first valve; a first pipeline for interconnecting saidfirst valve, said input/output vapor line of said supply tank and saidinput/output vapor line of said intermediate tank; a second valve; and,a second pipeline for interconnecting said input/output liquid line ofsaid supply tank, said second valve and said input/output liquid line ofsaid intermediate tank.
 17. A low-loss supply system for filling acontainer for liquified gas as claimed in claim 16 wherein said secondinterconnecting means comprises:a third valve; a fourth valve havingfirst and second terminals on a first side and first and secondterminals on a second side, the first terminal on said first sideconnected through an intermediate valve to the first terminal on saidsecond side and the second terminal on said first side connected throughanother intermediate valve to the second terminal on the second side; athird pipeline, said third pipeline interconnecting the input/outputliquid line of said supply tank, said third valve and the first terminalon the first side of said fourth valve; a fourth pipeline, said fourthpipeline interconnecting the input/output liquid line of saidintermediate tank to the second terminal on the first side of saidfourth valve; and, a fifth valve, interconnecting the first and secondterminals on the first side of said fourth valve, the first and secondterminals of the second side of said fourth valve connected to saidcontainer.
 18. A low-loss supply system for filling a container forliquified gas as claimed in claim 17 wherein said liquified gas isliquified oxygen.
 19. A low-loss supply system for filling a containerfor liquified gas as claimed in claim 17 wherein said supply tank andsaid intermediate tank are cryogenic storage vessels and wherein saidfirst, second, third and fourth pipelines are insulated pipelines. 20.The structure of claim 13 including condensing loop means for condensingvapors from at least one of said tanks.
 21. The structure of claim 20wherein said loop means is located so that condensed vapors are returnedto the liquid phase of one of said tanks.
 22. The structure of claim 20wherein said loop means is located inside of one of said tanks.
 23. Thestructure of claim 13 including:a source of condensing fluid; acondenser; and means for directing said condensing fluid to saidcondenser located so that vapors from at least one of said tanks isbrought into contact therewith and causes said vapors to condense. 24.The structure of claim 23 wherein said condenser is located so thatcondensed vapors are returned to the liquid phase of one of said tanks.25. The structure of claim 23 wherein said condenser is located insideof one of said tanks.
 26. The structure of claim 13 wherein said secondinterconnecting means includes a pipeline for connecting the vapor phaseof said container to the vapor phase of said intermediate tank.
 27. Thestructure of claim 26 including a one-way valve in said pipeline forpreventing the flow of gas in said pipeline in a direction out of saidintermediate tank.
 28. The structure of claim 26 including:a source ofcondensing fluid; a condenser, and, means for directing said condensingfluid to said condenser located so that vapors from at least one of saidtanks is brought into contact therewith and causes said vapors tocondense.
 29. The structure of claim 28 wherein said condenser islocated so that condensed vapors are returned to the liquid phase of oneof said tanks.
 30. The structure of claim 29 wherein said condenser islocated inside of one of said tanks. .Iadd.
 31. A low-loss method offilling a container for liquified gas from a supply system comprisingthe steps of:transferring liquid from a first vessel into a secondvessel, and transferring vapor from said second vessel to said firstvessel whereby the pressure between said first and second vesselsremains equalized as said liquid is transferred; isolating said firstvessel from said second vessel; connecting said second vessel and saidcontainer for liquified gas to equalize the pressure between said secondvessel and said container for liquified gas; connecting said firstvessel to said container for liquified gas to permit vapor to flowtherebetween; vapor thereby being permitted to flow from said containerfor liquified gas into said first vessel and liquid thereby beingpermitted to flow from said second vessel into said container forliquified gas..Iaddend..Iadd.
 32. The method of claim 31 including thestep of permitting the pressure of said second vessel to become higherthan the pressure of said container for liquified gas. .Iaddend. .Iadd.33. A pump-free low-loss supply system for filling a container forliquified gas comprising: a supply tank for housing said liquified gas;an intermediate tank for temporarily storing said liquified gas; firstinterconnecting means for interconnecting said intermediate tank to saidsupply tank for allowing liquid to flow by gravity from said supply tankto said intermediate tank and vapor to flow from said intermediate tankto said supply tank; and second interconnecting means forinterconnecting said intermediate tank and supply tank to said containerso as to allow liquid from said intermediate tank to flow into saidcontainer and vapor from said container for liquified gas to flow intosaid supply tank, said liquid thereby being transferred pump-free fromsaid supply tank to said container. .Iaddend..Iadd.
 34. The system ofclaim 33 including means for raising the pressure of said intermediatetank above the pressure of said container for liquified gas. .Iaddend.